The project was supported by the National Natural Science Foundation of China(21403070);National Key Research and Development Program of China(21573073);Shanghai Leading Academic Discipline Project(2017YFA0403102);The project was supported by the National Natural Science Foundation of China(21403070);上海重点学科建设项目(B409)

Small-sized zeolite ZSM-5 for a wide SiO2/Al2O3 ratio range was prepared using a small amount of colloidal silicalite-1 as the active seeds. The thus-prepared small-sized ZSM-5 samples have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption-desorption analysis, temperature-programmed ammonium desorption (NH3-TPD) analysis, and adsorbed pyridine infrared spectroscopy (Py-IR). The use of the active silicalite-1 seeds was effective in directing the reaction towards the formation of the MFI phase, avoiding the impure phases and reducing the crystal sizes. The prepared sample exhibited aggregated morphologies when a lower ratio of starting batch SiO2/Al2O3 (SiO2/Al2O3 ratio = 30) was used. The aggregates, with the size of ~500 nm, were formed with nano-sized primary crystals 50 nm in size, possessing large external surface area (84.9 m2·g−1) and secondary pore volume (0.22 cm3·g−1) and relatively regular mesopores. Different morphologies could be observed when the SiO2/Al2O3 ratio was increased (SiO2/Al2O3 ratio = 60–120). ZSM-5 with the size of 200 nm could be prepared, with the external surface area and the secondary pore volume being ~60 m2·g−1 and 0.10 cm3·g−1, respectively. It should be highlighted that all the prepared samples could be directly ion-exchanged to obtain the acidic H-form samples without complete blocking of the micropores due to the low dose of the organic structure-directing agent. The obtained acidic H-form samples exhibited acidic properties similar to the samples ion-exchanged after calcination and the conventional ZSM-5 possessing similar SiO2/Al2O3 ratio, showing catalytic performance comparative to the catalytic conversion of methanol to olefins. Compared with conventional methods, this method largely reduced the use of organic templates and avoided the subsequent combustion before ion-exchange. The method is green and cost-effective, possessing wide potentials in the industrial processes.